Enhancement of antimicrobial and long-term biostability of the zinc-incorporated hydroxyapatite coated 316L stainless steel implant for biomedical application

Antimicrobial hydroxyapatite (HAp) nanoparticles with different concentrations (0, 3, and 6 mol%) of zinc were prepared by the ultrasonication process. The prepared nanoparticles and chitosan (CTS) composite were coated on 316L stainless steel implant by spin coating technique. The powder samples were characterised by particle size analyser, X-ray fluorescence, and X-ray diffraction studies. The morphology of the coating was investigated by scanning electron microscopy. The diameter of the particle size decreased with increase in the concentration of zinc in HAp structure. The structure of the coated implant was found to be uniform without any cracks and pores. Antimicrobial activity of the composites against Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumonia, Salmonella typhi and Pseudomonas aeruginosa was analysed. The results showed that the increase in the concentration of zinc enhances the antimicrobial properties of 316L stainless steel implant. The stability of the implant in physiological environment was characterised by electrochemical impedance spectroscopy and polarisation analysis. The higher concentration of the ZnHAp/CTS composite shows higher corrosion resistance than that of the HAp/CTS-coated implant. This study shows that the coating provides corrosion resistance to the stainless steel substrate in simulated body fluid (SBF). The in vitro bioactivity study of the coated samples immersed in SBF solution confirms the formation of bone-like apatite layer on the surface of the implant. Thus, highly biocompatible ZnHAp/CTS-coated materials could be very useful in the long-term stability of the biomedical applications.     

Preparation of High Flexible Composite Film of Hydroxyapatite and Chitosan

Summary  Microscale hydroxyapatite (HAp), a well-known biocompatible substance for the regeneration and reinforcement of damaged bones, was composited with chitosan as a counter-polymer to produce a film with both biocompatibility and flexibility. Homogeneously dispersed solutions of microscale HAp powder and chitosan with various concentrations of HAp and chitosan were prepared in an attempt to optimize the characteristics of the film at room temperature using a molding method. The physiochemical and morphological properties of the prepared film were analyzed by thermal gravimetric analysis, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The prepared film showed high flexibility with homogeneous distribution of chitosan powders in the whole film. The results suggest that a biocompatible film of microscale HAp can be applied in various fields, such as the surface modification of bone implants, regeneration of damaged bones, osteoporosis to improve biocompatible interface between osteoblast cells and microscale inorganic materials, and to improve the osteoconductivity of bone regeneration     

Synthesis of hydroxyapatite/poly(vinyl alcohol phosphate) nanocomposite and its characterization

Hydroxyapatite (HAp)/poly(vinyl alcohol phosphate) (PVAP) nanocomposite has been prepared using a solution‐based method varying HAp from 10 to 60% (w/w). X‐ray diffraction, Fourier transform infrared absorption spectra (FTIR), and thermal analysis have indicated the presence of bonding between HAp particles and PVAP matrix. Transmission electron microscope analysis shows the needle‐like crystals of HAp powder having a diameter of 6–10 nm and a length of 26–38 nm. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. Particle size distribution analysis shows the narrow distribution of hydrodynamic particles in the polymer matrix. The tensile stress–strain curves show the improvement in mechanical properties of the composites with increase in amount of HAp particles loading. The composites along with polymer are highly hemocompatible. The use of PVAP promotes the homogeneous distribution of particles on the polymer matrix along with strong particle–polymer interfacial bonding, which has supported the improvement in mechanical properties of the composites. The prepared HAp/PVAP composite with uniform microstructure would be effective to act as a potential biomaterial. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Sodium dodecyl sulfate mediated microwave synthesis of biocompatible superparamagnetic mesoporous hydroxyapatite nanoparticles using black Chlamys varia seashell as a calcium source for biomedical applications

Designing biocompatible superparamagnetic mesoporous nanoparticles for advanced healthcare applications has received much attention. In this research, we have synthesized intrinsic mesoporous superparamagnetic hydroxyapatite (HAp) nanoparticles using bio-waste of black Chlamys varia seashell as a calcium source by sodium dodecyl sulfate (SDS)–enabled microwave-assisted synthesis approach. The synthesized Fe-doped HAp nanoparticles were characterized using various characterization techniques to know the phase purity and morphological features. The incorporation of Fe greatly affected the morphology of HAp nanoparticles without affecting their crystalline phase. Superparamagnetic behavior was observed with the incorporation of Fe in the HAp nanoparticles. Further, saturation magnetization was enhanced with higher incorporation of Fe ions. The cytotoxicity studies of the synthesized pure and Fe-doped HAp samples conducted using a human osteoblasts cell line (MG63), which indicated that Fe-doped HAp nanoparticles are biocompatible. Further, antibacterial activity analysis also confirmed their excellent antibacterial performance against different pathogens. Hence, SDS-enabled microwave-assisted synthesis approach using seashell as a calcium source would be a better approach for the production of intrinsic mesoporous superparamagnetic HAp nanoparticles for various biomedical applications, such as drug targeting, hyperthermia cancer therapy, and magnetic resonance imaging.     

Silica coated ferrite nanoparticles: Influence of citrate functionalization procedure on final particle morphology

In this paper, magnetic nanoparticles (Fe₃O₄ and NiFe₂O₄) were coated with a biocompatible silica shell via hydrolysis and condensation of tetraethyl orthosilicate (TEOS) by the Stöber process. Magnetic nanoparticles, prepared by chemical co-precipitation from iron and nickel salts, were functionalized with citric acid, in order to provide their deagglomeration and to enable their coating with silica. The parameters of the functionalization procedure were varied (concentration–pH and type of treatment), in order to examine if and how this particular step of preparation affects the final morphology of the core-shell particles. Transmission electron microscopy, zeta potential and particle size measurements revealed that the morphology and the size of obtained core shell particles depend significantly on the core particle size, and thus on the parameters of the functionalization step.     

Ni-P-PTFE复合镀层对颗粒污垢沉积特性影响研究

为探究Ni-P-PTFE复合镀层对颗粒污垢沉积特性的影响,利用化学镀工艺在碳钢表面制备Ni-P-PTFE复合镀层,以TiO₂纳米颗粒为研究对象,通过实验和理论分析的方式研究了不同表面能（PTFE浓度）下Ni-P-PTFE复合镀层在TiO₂悬浮液中的颗粒污垢沉积特性。结果表明：相比于碳钢试样,Ni-P-PTFE复合镀层对于TiO₂颗粒沉积具有较好的抑制效果。随着PTFE浓度的增加,复合镀层的表面能降低,污垢沉积量呈下降趋势,在表面能为26.8 mJ/m²（PTFE=12 ml/L）时,TiO₂颗粒污垢在Ni-P-PTFE复合镀层的沉积量最小。实验结果与应用扩展的DLVO理论计算出的最佳表面能结果相一致,也为针对不同类型颗粒在换热表面的沉积的抑垢提供了指导施镀的依据。     

Ni-P-PTFE复合镀层对颗粒污垢沉积特性影响研究

为探究Ni-P-PTFE复合镀层对颗粒污垢沉积特性的影响,利用化学镀工艺在碳钢表面制备Ni-P-PTFE复合镀层,以TiO₂纳米颗粒为研究对象,通过实验和理论分析的方式研究了不同表面能（PTFE浓度）下Ni-P-PTFE复合镀层在TiO₂悬浮液中的颗粒污垢沉积特性。结果表明：相比于碳钢试样,Ni-P-PTFE复合镀层对于TiO₂颗粒沉积具有较好的抑制效果。随着PTFE浓度的增加,复合镀层的表面能降低,污垢沉积量呈下降趋势,在表面能为26.8 mJ/m²（PTFE=12 ml/L）时,TiO₂颗粒污垢在Ni-P-PTFE复合镀层的沉积量最小。实验结果与应用扩展的DLVO理论计算出的最佳表面能结果相一致,也为针对不同类型颗粒在换热表面的沉积的抑垢提供了指导施镀的依据。     

Core‐shell structured ferrite‐silsesquioxane‐epoxy nanocomposites: Composite homogeneity and mechanical and magnetic properties

Epoxy‐based composites of ferrite nanoparticles (50 nm) with 3‐glycidoxypropyl‐ (GPTMS), aminopropyl‐ (APTMS), or methyl‐silsesquioxane (MTMS) coatings are reported. The GPTMS coatings (30‐nm thick) allowed uniform particle dispersion in the epoxy and prevented sedimentation of the nanoparticles, whereas the APTMS‐coated particles formed agglomerates, leading to particle sedimentation. The particles with the thinnest coating (MTMS – 3 nm) agglomerated in the composites without sedimentation. The composites based on GPTMS‐coated particles showed higher fracture toughness than the composites based on MTMS‐coated particles. The uniformity and thickness of the coatings were related to alcohol composition of the coating media. Coating removal by a novel ultrasonic etching allowed precise determination of the effective ferrite content in the coated nanoparticles. A markedly lower coercivity for nanoparticles without coatings as compared with the nanoparticles with thicker coatings was observed. The saturation magnetization and the coercivity of the composites were independent of coating and casting procedures. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Enhanced mechanical properties of acrylate based shape memory polymer using grafted hydroxyapatite

In the present study, the effect of grafted and ungrafted hydroxyapatite (HAp) filler on the mechanical properties of acrylate based shape memory polymer (SMP) composite is reported. HAp is grafted with polyethylene glycol methacrylate (PEGMA) monomer to avoid agglomeration and the same is embedded as reinforcement in tBA – PEGDMA matrix (70 wt% tBA: tert-butyl acrylate +30 wt% PEGDMA: polyethylene glycol dimethacrylate). The grafting process improved the interfacial interactions of the particles, dispersed in the polymer system and subsequently enhanced the mechanical properties of the shape memory polymer composites. The morphology of HAp particles is investigated by field emission scanning electron microscopy. The mechanical properties of SMP composites are evaluated at room temperature and above glass transition temperature (Tg) with grafted and ungrafted HAp particles. The addition of grafted HAp significantly improved the tensile strength (40%) and shape recovery rate (25%) of the SMP composite when compared to the SMP composite containing ungrafted HAp. SMP composite containing grafted HAp exhibited higher cell viability compared to the neat SMP and the SMP composite containing ungrafted HAp.     

Fabrication of sustained‐release and antibacterial citronella oil‐loaded composite microcapsules based on Pickering emulsion templates

In this work, the citronella oil (CTO)‐loaded composite microcapsules with hydroxyapatite (HAp)/quaternary ammonium salt of chitosan (HACC)/sodium alginate (SA) shells are facilely and effectively fabricated by templating citronella oil‐in‐water Pickering emulsions, which are stabilized with HAp nanoparticles. The microcapsule composite shells are prepared by the electrostatic adsorption of HACC and SA, and then chelation interaction of alginate and Ca²⁺ ions released from HAp nanoparticles. Scanning electronic microscope observation shows that the microcapsules have a spherical shape. Thereafter, Fourier transform infrared spectroscopy and thermal gravimetric analysis results indicate that CTO is successfully loaded into the microcapsules, and the related CTO‐loaded microcapsules possess the thermal stability. Moreover, the in vitro release study of CTO shows that the microcapsules have sustained release activity, and the related CTO release profiles can be well described by Rigter–Peppas model. The antimicrobial assays of microcapsules display the antibacterial effect of CTO‐loaded microcapsules against Staphylococcus aureus and Escherichia coli. Overall, this study opens up new potentiality for unstable active ingredient as an environmental friendly and ingenious microencapsulation in food and agriculture applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46386.     

Synthesis and Characterization of Hydroxyapatite/Poly(Vinyl Alcohol Phosphate) Nanocomposite Biomaterials

A hydroxyapatite (HAp)/poly(vinyl alcohol phosphate) (PVAP) nanocomposite has been prepared by a chemical method by varying the HAp content by 10–60% (w/w). The bonding between HAp and PVAP has been investigated through Fourier transform infrared absorption spectra, X-ray diffraction, and thermogravimetric analyses. Transmission electron microscopy study shows a homogeneous dispersion of nanoparticles in the polymer matrix. Scanning electron microscopy study shows enhancement of the surface roughness of the composite with an increase in the nanoparticle content. The mechanical properties of the composites improve significantly with an increase in the HAp content. The HAp/PVAP nanocomposite prepared may have bone–implant applications.     

Synthesis of novel sunflower-like silica/polypyrrole nanocomposites via self-assembly polymerization

Novel sunflower-like organic-inorganic composites consisting of spherical silica and smaller conductive polypyrrole particles were successfully prepared through an in situ self-assembly polymerization process by choosing chitosan as a modifying agent of silica surface. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that on the surface of individual silica particle polypyrrole nanoparticles were anchored perfectly. The sunflower-like silica-polypyrrole composites exhibited conductivity of 8 S cm⁻¹ and colloid stability because of the special surface morphology. Adsorbed chitosan chain may play a dual-role of both providing the active sites for formation of the polypyrrole particles on silica and acting as a stabilizer of the silica-polypyrrole particles. Hydrogen-bonding interaction between the acetylamino group of chitosan and hydrogen atom on nitrogen of polypyrrole is a determining parameter in the former case.     

Appropriate thickness of pyrolytic carbon coating on SiC fiber reinforcement to secure reasonable quasi-ductility on NITE SiC/SiC composites

Pyrolytic carbon (PyC) coating of silicon carbide (SiC) fibers is an important technology that creates quasi-ductility to SiC/SiC composites. Nano-infiltration and transient eutectic-phase (NITE) process is appealing for the fabrication of SiC/SiC composites for use in high temperature system structures. However, the appropriate conditions for the PyC coating of the composites have not been sufficiently tested. In this research, SiC fibers, with several thick PyC coatings prepared using a chemical vapor infiltration continuous furnace, were used in the fabrication of NITE SiC/SiC composites. Three point bending tests of the composites revealed that the thickness of the PyC coating affected the quasi-ductility of the composites. The composites reinforced by 300?nm thick coated SiC fibers showed a brittle fracture behavior; the composites reinforced 500 and 1200?nm thick PyC coated SiC fibers exhibited a better quasi-ductility. Transmission electron microscope research revealed that the surface of the as-coated PyC coating on a SiC fiber was almost smooth, but the interface between the PyC coating and SiC matrix in a NITE SiC/SiC composite was very rough. The thickness of the PyC coating was considered to be reduced maximum 400?nm during the composite fabrication procedure. The interface was possibly damaged during the composite fabrication procedure, and therefore, the thickness of the PyC coating on the SiC fibers should be thicker than 500?nm to ensure quasi-ductility of the NITE SiC/SiC composites.     

Synthesis of hydroxyapatite nanoparticles using surface carboxyl-functionalized carbon dots as template

Carbon dots (CDs), which are discrete, nearly spherical nanoparticles with sizes below 10?nm and large amounts of carboxylic acid moieties on the surface, have been proposed as an ideal template candidate for heterogeneous nucleators to regulate hydroxyapatite (HAp) nucleation and growth. In this paper, small HAp nanoparticles formed on carboxyl-functionalized CDs in situ were fabricated via the hydrothermal method. Investigation for the corresponding morphologies and detailed formation mechanisms of samples were conducted by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and Rietveld refinement. The optimum size and crystallinity of HAp particle had been obtained in the preparation when the additive content of CDs was 1.11?g/L. Moreover, results also suggested that CDs were served as nucleators in the HAp particles. Therefore, a novel synthetic strategy is presented for small HAp nanoparticles using CDs as template.     

A study of the electrophoretic deposition of bioactive glass-chitosan composite coating

Bioactive glass is coated on implant's surface to improve corrosion resistance and osseointegration, when placed in the body. Bioactive glass particles were synthesized through a sol-gel process and deposited along with chitosan to form a composite coating on a stainless steel substrate using electrophoretic deposition technique. Stable suspensions of chitosan-bioactive glass were prepared using bioactive glass particles (<1 μm) and 0.5 g/l chitosan solution. The influence of ethanol-water ratio on deposition yield was investigated. For all process conditions, best results were achieved with suspension of 30 vol% water in ethanol-water containing 2 g/l bioactive glass. FTIR studies showed that chitosan was absorbed on ceramic particle surface via hydroxyl and amid bonds. In order to evaluate the coating, its structure and electrochemical properties were studied. It was concluded that increasing the process voltage led to an increase in particle size and porosity, but induced cracks in the coating. In the presence of the polymer-bioactive glass coating, current density in artificial saliva was decreased by 52% and corrosion potential shifted toward more noble values.     

Dielectric,magnetic, and mechanical properties of composites consisting of biopolymer chitosan matrix and hybrid spinel/cellulose filler

The composites consisting of a biopolymer chitosan matrix and hybrid spinel/cellulose filler were prepared by solvent casting method whereas the spinel CoFe₂O₄ was obtained by mechanical synthesis followed by thermal annealing. Incorporation of cellulose to the spinel – chitosan composite significantly modified dielectric, magnetic and mechanical properties of a composite consisting of the biopolymer with hybrid filler. In dielectric response the presence of the filler in the chitosan matrix hindered the molecular motion. The lowering of the activation energy and the cooperativity of the motion was observed. According to the magnetic properties, addition of cellulose to the filler enhanced coercivity field H_c in comparison to the pure spinel powder from value 0.1453 to 0.2033?T. In mechanical properties incorporation of the filler resulted in improvement of Young's modulus and tensile strength in comparison to unfilled chitosan. For composites with nanocellulose filler tensile strength was over two times higher than for chitosan.     

Studies on novel bioactive glasses and bioactive glass-nano-HAp composites suitable for coating on metallic implants

A series of novel zinc oxide (ZnO) containing bioactive glass compositions in SiO₂-Na₂O-CaO-P₂O₅ system and composite with hydroxyapatite (HAp) nano-particles were developed and applied as coating on Ti-6Al-4V substrates. The bioactive glasses and their composites were also processed to yield dense scaffolds, porous scaffolds and porous bone filler materials. The coating materials and the coatings were characterized and evaluated by different in vitro techniques to establish their superior mechanical properties. The cytotoxicity test of the coating material, porous and dense scaffolds and coated specimens showed non-cytotoxicity, biocompatibility and promising in vitro bioactivity for all tested samples. The dissolution behaviour studies of the bioactive glasses and the composites in simulated body fluid showed promising in vitro release pattern and bioactivity for all tested samples. Addition of nanosized HAp improves mechanical properties of the bioactive glass coating without affecting the in vitro bioactivity.     

Processing and properties of nano‐ and macro‐hydroxyapatite/poly(ethylene‐co‐acrylic acid) composites

Hydroxyapatite (HAp)/poly(ethylene‐co‐acrylic acid) composites have been synthesized by a solution‐based method, using nanosized (n‐HAp) and coarse hydroxyapatite (c‐HAp) particles, respectively. X‐ray diffraction study has indicated the development of compressive and tensile stresses in composites because of the thermal expansion mismatch between the particles and polymer matrix. Fourier transform infrared absorption spectra and thermal analysis have showed the presence of strong interfacial bonding between the particles and polymer. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. A comparison in mechanical properties between composites prepared with n‐HAp and c‐HAp particles, respectively, has been studied. Nanosized particles contribute excellent improvement of mechanical properties of the composites rather than the coarse particles. The uniform dispersion of HAp particles, followed by the improvement in mechanical properties of the composite, provides a means of preparing HAp/polymer composites for low load‐bearing implant applications. POLYM. COMPOS., 27:633–641, 2006. © 2006 Society of Plastics Engineers     

Characterization and preparation of polyion complex composite membranes for the separation of methyl tert‐butyl ether/methanol mixtures

A series of polyion complex (PIC) composite membranes composed of sodium alginate (SA) polyanion and chitosan polycation were prepared by varying the ratio of concentration. The interaction between SA and chitosan was investigated by FTIR, SEM, and X‐ray analysis and was related to mechanical properties and the swelling phenomenon. The overall PIC composite membranes showed the following results: the total thickness of the coating layer was thicker than that of pure SA composite, and increased with increasing the concentration of chitosan solution during PIC formation. This result was attributed to the diffusion of chitosan molecules from the liquid solution into the SA matrix, and the incorporation with SA molecules. For the PIC membranes prepared with different concentrations of polymer solution, their structural differences could not be detected from IR spectra but their morphological differences could be noticeably found from SEM. Furthermore, the amorphousness of PIC membranes and their elongation properties at break increased significantly as a function of polymer contents, whereas the tensile modulus decreased because of the physical transition effect. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 714–725, 2002     

Surface compatibility in a carbon-alloy composite and its influence on the electrochemical performance of Li/ion batteries

Carbon-alloy composites were prepared by coating carbon materials with different surfaces with Sn, Sb or SnSb. The SnSb-hard carbon spherule (HCS) composite electrode shows the best cycling performance. The matching of crystalline parameters between SnSb and the carbon ensures a good dispersion of SnSb alloy on the surface. The high density of the nucleation centers on the HCS surface leads to a small SnSb crystallite size. Open pores on the surface of HCS, into which the alloy crystals are allowed to grow, act as pinning centers, which further stabilize the composite. These three factors are supposed to be responsible for the best cyclic performance of SnSb-HCS composite. The latter two factors also result in a large BET surface area, which leads to a large initial irreversible capacity loss, because more solid electrolyte interface film is formed. It seems that the best cyclic performance and the highest initial efficiency are paradoxical in the SnSb-carbon composite. Further surface modification should be conducted to obtain better electrode materials.